AIM: To compare the accuracy of transvaginal ultrasound, transvaginal color Doppler, hysterosonography, and three-dimensional ultrasound in the detection of septate uteri. To evaluate obstetrical prognosis of the septate uterus and to assess the reproductive outcome following operative hysteroscopy. PATIENTS AND METHODS: Four hundred and twenty infertile patients undergoing hysteroscopy were evaluated prospectively during a 4 year period. Transvaginal ultrasound and color Doppler were performed in all patients, whereas hysterosonography and three-dimensional ultrasound were used in 76 and 86 patients, respectively. RESULTS: The sensitivity of transvaginal ultrasound and transvaginal color Doppler in the identification of the septate uterus was 95.0% and 99.3%, respectively. Color and pulsed Doppler studies of the septal area revealed vascularity in 71.2%. The sensitivity of hysterosonography and three-dimensional ultrasound in the detection of the septate uterus were 100% and 93.6%, respectively. However, the latter method predicted the existence of a congenital uterine defect in all the patients with septate uterus, but was inaccurate in differentiating it from other fusion anomalies. The pregnancy rate in 116 patients following the operative hysteroscopy for an intrauterine septum in a prospective follow-up period of 24 months was 50.9%: 44 patients (74.6%) had term deliveries, 11 (18.6%) had first trimester abortion, and 4 (6.8%) had preterm delivery. CONCLUSIONS: Transvaginal color Doppler and hysterosonography are highly accurate diagnostic tools for preoperative evaluation of the uterine cavitary defects. Three-dimensional ultrasound increases the accuracy of conventional two-dimensional transvaginal scan, allowing precise reconstruction of the uterine cavity. Removing the intrauterine septum in patients suffering from infertility and recurrent pregnancy wastage is beneficial.